The present invention relates to a semiconductor apparatus and a manufacturing method thereof and relates, in particular, to a semiconductor apparatus including a semiconductor device brought into junction with a circuit substrate comprising a heat sink and a manufacturing method thereof.
A semiconductor apparatus comprising a heat sink, a substrate stacked and adhered to the heat sink, and a semiconductor device mounted on a circuit pattern of the substrate is known. Heat generated by the semiconductor device is conducted to the heat sink through the substrate from the bottom surface of the semiconductor device and, thereby, is dissipated, that is, released. However, when a semiconductor apparatus simply reduces in size, the contact area between the semiconductor device and the substrate reduces. Consequently, a conduction amount, from the bottom surface of the semiconductor device, of heat generated by the semiconductor device reduces. Therefore, the semiconductor device is not cooled smoothly. Thus, Japanese Laid-Open Patent Publication No. 2000-323630 proposes to mount an auxiliary substrate for heat release in a portion in the surface of a semiconductor on the opposite side from the substrate stacked and adhered to a heat sink. A radiation fin or a water-cooled heat sink is mounted on the auxiliary substrate.
FIG. 13A illustrates a semiconductor module 51 disclosed in Japanese Laid-Open Patent Publication No. 2002-270765. The semiconductor module 51 used in an electric power conversion system is intended to restrain a drastic temperature increase of a semiconductor device 54 in the overload state. The semiconductor device 54 is provided on a metal substrate 52 with an insulating substrate 53 in between. A pair of heat accumulators 55 is provided immediately above and in the vicinity of the semiconductor device 54. The heat accumulator 55 houses substance, for example, low melting point metal, which changes in phase from solid to liquid at a temperature slightly lower than the upper limit temperature at which the semiconductor device 54 can be used. The low melting point metal absorbs heat of the semiconductor device 54 temporarily and thereafter releases heat. Heat generated in the semiconductor device 54 is normally conducted only to a cooler (not shown) through a metal substrate 52. However, in the case where the semiconductor device 54 is in the overload state with which cooling capability of the cooler cannot cope sufficiently, the heat accumulator 55 accumulates the excess heat temporarily and thereafter the heat is conducted to the cooler.
FIG. 13B illustrates a junction apparatus disclosed by Japanese Laid-Open Utility Model Publication No. 5-13660. The junction apparatus is intended for production of a thermoelectric module by including a plurality of thermoelectric devices coming into junction with a substrate with high-frequency induction heating. High-frequency induction heating can bring a ceramic member into junction with a metal member and bring electronic parts into junction with a substrate. A junction apparatus comprises a stand 61, a pressuring jig 63 pressuring the substrate 62, and a high-frequency heating coil 64 provided around the pressuring jig 63. The pressuring jig 63 is a weight having an end surface in contact with the substrate 62. A carbon sheet 65, a thermoelectric device 66 and a substrate 62 are sequentially arranged on the stand 61. When the high-frequency heating coil 64 causes the pressuring jig 63 to undergo induction heating, that is, high-frequency heating in the state where the substrate 62 is being pressurized by the pressuring jig 63, heat generated by the pressuring jig 63 is conducted to the substrate 62, the thermoelectric device 66 is brought into junction with the substrate 62. By arranging solder and brazing filler metal between the substrate 62 and the thermoelectric device 66, the thermoelectric device 66 is soldered or brazed to the substrate 62.
Generally, a semiconductor device includes an electrode on the side opposite from the junction surface with the substrate. However, as described above, an auxiliary substrate is mounted on a semiconductor device of the above described Japanese Laid-Open Patent Publication No. 2000-323630. A radiation fin or a water-cooled heat sink is thermally connected to the auxiliary substrate. Therefore, in order to connect a wire or a lead to an electrode being present on the upper surface of a semiconductor device, a special configuration for preventing the wire or the lead from interfering with the radiation fin or a water-cooled heat sink is required. Consequently, the work for bringing the wire or the lead into junction with an electrode is cumbersome.
Comparing with such a configuration of Japanese Laid-Open Patent Publication No. 2000-323630, the above described cooler (not shown) of the above described Japanese Laid-Open Patent Publication No. 2002-270765 can preferably deal with heat generation of the semiconductor device 54 in the non-overload state, for example, the normal state illustrated in FIG. 13A. Therefore, an increase in size of the cooler is restrained. However, the heat accumulator 55 is required to house substance capable of changing from the solid phase to the liquid phase, that is, low melting point metal. Therefore, due to measures for thermal stress or convenience on fabrication of the heat accumulator 55, space is assumed to take place inside the heat accumulator 55 in the case where the low melting point metal is in the liquid phase. Thus, even if the heat accumulator 55 is used as an electrode, the container of the heat accumulator 55 actually functions as an electrical conduction route to make the current uneven between the center and the periphery of the semiconductor device 54. Therefore, the heat accumulator 55 cannot be used as an electrode. Moreover, the wire or the lead to be connected to an electrode needs to be arranged so as not to interfere with the heat accumulator 55. In addition, in the case of mounting a semiconductor module 51 on a vehicle, if low melting point metal inside the heat accumulator 55 occasionally comes into the solid phase in a biased state when a vehicle is accelerated and decelerated, a vehicle runs around a curve, a vehicle shakes or a vehicle inclines, then the subsequent heat accumulating operation may become nonuniform.